Nowadays, telephone communication is not particularly surprising, given the sad fact that the smartphone is most often used for entertainment purposes. But more recently, the phone was an amazing, marvelous and... rather bulky device. One of its elements, namely the Pupin coil, will be discussed in the article.
How the Pupin coil appeared
2 serious problems prevented the laying of telephone communications over considerable distances: the appearance of inductance and capacitance in the wires. These phenomena created a barrier to the signal, and the rapid development of communication stalled a little.
The path "from the opposite" became an ingenious solution. The famous English engineer - Oliver Heaviside, who reached many heights thanks to the gift for self-education, proposed to increase the capacity of the line. To do this, it was enough to install inductors along the entire length of the line.
Due to not very friendly relations with the chief specialist of the British General Mail - Pierce, Oliver did not file a patent for his own invention. But exactly 10 years later, exactly the same coil was presented to the public by Professor Pupin, who was later assigned the rights to this invention.
The principle of operation of the Pupin coil
The Pupin Coil is a standard inductor designed to reduce frequency attenuation and thus “flatten” the line in the range from 0.3 to 3 kHz. A completely simple invention made it possible to increase the length of the line to almost 100 km.
In order for the Pupin coil to work correctly, certain requirements must be met:
- The inductance of the coil should be at least 2 times higher than the inductance of the line itself - from 1 to 140 mH.
- The products should be installed at a certain distance from each other - from 300 m to 2 km.
Otherwise, the Pupin coil has proven itself perfectly, and is still used in some sparsely populated areas.
The main disadvantage
There are no perfect mechanisms or radio components. If for the low frequencies the Pupin coil serves as a filter, then for the high frequencies (for example, modern DSL and ISDN), on the contrary, it is the cause of their strong distortion. That is why, with the rapid development of telephone lines, Pupin's coils had to be urgently found and removed.
What the Pupin coil consists of
By its manufacture, the Pupin coil is not expensive (neither in terms of funds, nor in terms of time), therefore, in the last century, many radio amateurs independently assembled and wound such products.
Pupin's coil consists of a ferromagnetic core, always in the form of a ring, with a copper insulated wire wound around it. For this design it is best to use a ferromagnetic material because of its temperature dependence of magnetization. And they use a special wire - winding.
Modern Pupin coils differ significantly from the first products and more resemble in appearance a standard telephone socket.